3/20 Abdominal Pain - Corbett

Question 1

viscera and visceral peritoneum

vs

parietal peritoneum

Answer 1

viscera/visceral peritoneum : from splanchnic layer of lateral plate mesoderm

• peritoneal covering
• hollow viscus
• mesentery

→ → visceral pain from irritation of visceral peritoneum, HOLLOW viscera, and mesentary

• from MECHANICAL STIMULI (tension, traction, distention) and CHEMICAL STIMULI (ischemia, infl)
• does NOT lateralize (bc viscera are embryologically midline structures) → pain perceived in midline

innervation: autonomic nervous system (PSNS, SNS)]

parietal peritoneum : from somatic layer of lateral plate mesoderm

• peritoneal lining of abd wall

→ → parietal/somatic pain from irritation of parietal peritoneum

why different?

embryological origins are different!

Question 2

fore vs mid vs hindgut structures and blood supply

Answer 2

foregut : celiac

• esophagus
• stomach
• duodenum to CBD
• gallbl, pancreas, liver

midgut : SMA

• duodenum
• small intestine
• apendix
• R colon and prox transverse colon

hindgut : IMA

• dist transverse colon
• L colon
• rectum

Question 3

why is visceral pain poorly localized?

Answer 3

• low density of visceral pain receptors
• viscero-visceral convergence of sensory info onto same neurons → input from visceral and somatic sensory fields end up converging on same neurons in dorsal horn and dorsal column nuclei

makes it hard to pinpoint where pain is originating from

• evoked more from hollow organs, from organ covering
• often accompanied by autonomic sx

Question 4

referred pain

Answer 4

visceral pain afferents are mapping onto spinal cord at same places that somatic afferents are mapping → synapse onto same neurons (“convergence”)

Question 5

peritonitis

Answer 5

inflammation of parietal peritoneum

• reactive hyperemia
• protein rich exudate in abdomen → accumulation
• emigration of leukocytes
• leads to inhibition of peristalsis

detected by nociceptors (somatic nerves)

• peritoneum of abd wall and pelvis: same nerves that supply abd wall musculature and skin (T7-L1)
• peritoneum of diaphram: phrenic nerve (C3-C5) and lower 6 intercostal/subcostal nerves

severe, well localized, lateralized, pain that’s worse with movement

→ leads to reflex contraction (rigidity/invol guarding) of corresponding segmental area of muscle/skin hyperthesia

Question 6

why is somatic pain more severe?

Answer 6

dense meshwork of free nerve endings, precise/fine mapping in CNS

Question 7

parietal peritoneum

vs

visceral peritoneum

• innervation
• location
• character
• stimulus

Answer 7

Question 8

parietal pain vs visceral pain

OPQRST

Answer 8

Question 9

acute abdomen causes

Answer 9

• peritonitis from inflammation, ischemia, perforation
  
  • ​ischemia: due to arterial occlusion, venous obstruction, general hypoperfusion (shock)
• small bowel obstruction

see involuntary contraction of abd musculature, rebound tenderness, percussion tenderness, cough tenderness

Question 10

bowel obstruction - body’s response? sequellae? causes?

Answer 10

1. reflex contraction (attempt to overcome obstruction)
2. fluid secretion

will lead to proximal dilation and eventually ischemia&perforation if untreated

most common causes = ABC

• adhesions (surgery = risk)
• bulgers (hernia)
• cancer (most common obstruction!)